For hours, Nabil ran back and forth with a crew of 15 others near the Egyptian museum, where the main battle took place. He threw stones, watched for snipers on an overpass; and slowly, but surely, his team "occupied" the opposing forces' turf. "We spent the night defending the square."

The rush of revolution has kept Nabil's adrenaline pumping. But he says his image of his fellow demonstrators is of peaceful and victimized individuals; it remains his conviction that Mubarak and Vice President Omar Suleiman are to blame for the violence. All that keeps him committed. "Of course, Mubarak sent those people last night," the doctor says, "He tried to scare people to go home." (See what the U.S. loses if Mubarak goes.)

State media, he laments, is spreading the President's lies. "And Mubarak is telling U.S. and other countries that if he goes, it will be radical Muslims in control." He knows that the Muslim Brotherhood is the group the government means. "But I've seen them in the community and here and they are so peaceful." Looking around at some of the bearded men and women in long, muted headscarves, he says "They are around us right now, by the way. But they are a minority."

At midday in the square, girls are wearing headbands in the color of the Egyptian flag. Demonstrators are passing out fruit. And a band has taken over a makeshift stage and sound system that people have lugged in through the checkpoints. A few young men, one with his head heavily bandaged, stand before a microphone and strum slowly on a guitar, as the crowd waves flags to the rhythm. "When the thief becomes a leader, you know you are in a country with democracy," the young singer croons satirically. "When the policemen kill the people, you know you're in a democracy." The crowd laughs. (See Fareed Zakaria's cover story: How democracy can work in the Middle East.)

"Down with Mubarak," the chorus goes, almost cheerfully, and several dozen men and women join the refrain: "Down with Mubarak, Fall, fall, fall!"

A man pulls Nabil away, over to the makeshift tent village on Tahrir's central green. The older woman leaning in the grass is pale; her eyes listless. Nabil crouches beside her and takes her pulse. "Look, you need to take her home," he said to her son, after establishing that the woman has hypertension and an unhealthy heart rate. "She's sick, take her home." At first, the man resists. "No, we're not going anywhere," he says. The family has been there for days; they don't want to leave until Mubarak has stepped down. Nabil persists; other activists join; and finally the family agrees to leave.

"You know what they're telling people on state TV? That ElBaradei is giving everyone 100 LE [Egyptian Lira] to be here, and a meal from Kentucky [fried chicken]," he shakes his head. The sun is starting to set. And a burst of gunfire crackles to the north; the first sign of clashes that would again consume Tahrir's northern inroad as night takes hold. Volunteers entering on the west side, from the Qasr al-Nil bridge, are bringing in blankets.

By nightfall, Nabil had finally gone home for a shower, leaving others to guard the square. His voice is hoarse. He plans to be back in Tahrir in time for Friday afternoon prayer, after which opposition activists are calling for another major demonstration. "I have to say to Mubarak: 'Thank you,'" Nabil says bitterly. "You made more people come here. You made the media see the truth."

"Now people are saying: 'we are more free, we have more courage.' Yesterday all of us knew we could die. But we knew it would be for a higher cause. God willing, it will continue until Mubarak goes. He has blood on his hands."